Amplifying system



Oct. 21, 1941.

SIGNAL INPUT A W. HAGEN AMPLIFYING SYSTEM v Filed Aug. 10, 1958 POM/ER SOURCE T0 POWER SOURCE INTEEMED/HTE 0R FINAL AMPLIFIER our/ ar Inventor:

h oyqany Hagen Patented Oct. 21, 1941 UNITED STATES PATENT OFFICE AMPLIFYING SYSTEM Application August 10, 1938, Serial No. 224,065 In Germany August 12, 1937 1 Claim.

The present invention relates to amplifying systems, and more specifically to intermediate stage and final stage amplifiers used for intelligence transmission over cable lines.

It is frequently necessary in connection with message transmission over cables by means of carrier frequency alternating currents to insert amplifiers either in the line itself or at the end thereof in order to compensate for the decreased amplitude of the alternating currents on account of the line attenuation. The same requirements exist when low frequency alternating message currents are directly transmitted over cables or other lines.

Certain inconveniences prevail in connection with such amplifying devices which must either be continually kept functioning so as to be ready to operate at each and every instant, or be continuously attended by an operator whose duty is to render the system effective for message or other reception. The first mentioned continuous operative condition requires a permanent current consumption, and moreover, considerable expenditure with respect to the necessary highefiiciency amplifying valves and other circuit elements.

It has been suggested to remotely control the amplifiers from the terminal station, but considerable difiiculties have been experienced in carrying out this idea. It is impossible at carrier frequency intelligence transmission and simultaneous utilization of the lines for low frequency current transmission to employ direct current or even alternating current impulses of low periodicity. On the other hand, high frequency impulses are rather disadvantageous since their intensity is very low at the control position, from which follows that they are hardly strong enough to operate a relay or similar elements which serve for rendering the apparatus under consideration effective.

The present invention has for its object to eliminate the above mentioned disadvantages. This is accomplished according to the main feature of the invention by the provision of a particular control amplifier which is continually ready to operate and which on receipt of given signal currents renders the entire amplifier system effective.

The particular control amplifier is constructed in accordance with a further feature of the invention so as to operate not only with utmost simple means but also with an extremely low amount of power. Moreover, this amplifier in volves a highly reliable operation.

The invention will be more readily understood from the following description taken in conjunction with the accompanying drawing, the single figure of which shows a wiring diagram according to one embodiment of the invention.

The intermediate or final amplifier system comprises a high frequency amplifier device (not shown) and a specific control amplifier illustrated in the accompanying drawing. The signal currents for the latter amplifier are impressed thereupon over the lines A and B. The control amplifier may, for example, consist of two valve stages I and 2. Tunable circuits 3 and 4 which are to be tuned to the frequency of the signal current or currents are connected to the grids of the valves l and 2, respectively. The control frequency may be located in the high frequency or in the low frequency spectrum. The current supply to the control amplifier may be an alternating current or a direct current source connected to the terminals C and D, This voltage is directly applied as anode potential to the anodes of the valves l and 2 and the serially connected filaments of these valves through the series resistances 5 and B. The grid biasing potentials for the valves are derived from a rectifier 1 parallel to the resistance 5 or from a potentiometer 8 across which is shunted a smoothing condenser 9. Signal currents arriving over the leads A and B are rectified and then applied to a relay HI forming part of the anode circuit of valve 2. The contact ll of the so operated relay in establishes a circuit which renders the main amplifying system active. This amplifier arrangement involves the advantages that it operates with a minimum of simple means and that it functions with an alternating current or a direct current supply and, moreover, that its power consumption is very low in continuous operation so that there is no necessity for providing means for feeding the apparatus from the mains supply.

The arrangement heretofore disclosed is preferably applicable to receiving devices which are remotely controlled, in public address systems for example. The arrangement is furthermore well adapted for effecting other switching or signalling functions.

What is claimed is:

An amplifying system comprising a signal input circuit, an amplifying device coupled to said input circuit and comprising an amplifying stage including a tube having a cathode, a filament, a control grid and an anode, a resistance connected in the filament circuit of said tube, a rectifier connected in parallel with said resistance and a connection for applying to said grid a biasing potential derived from said rectifier, an amplifier for signals from said signal circuit, a power source for said amplifier, and a relay in the output of said amplifying device for connecting said power source to said amplifier to render it operative in response to the receipt of signals over said signal input circuit.

WOLFGANG HAGEN. 

